Refrigerant never runs out or gets used up. It sounds to me that the compressor may be overheating and cutting out on internal overload until it cools down enough to start up again. To check pressures you would have to install a piercing valve on the suction line.

Tech2000 to make sure I follow. I will be able to monitor the pressure by installing a piercing value on the suction line....what should an optimal pressure be? If I do find the compressor is overheating....what can be done to fix the issue?

How hard and costly would it be to install an entirely new compressor? Space might be somewhat of an issue...I will look into that tonight

Well if it doesn't have the pressure information on the rating plate, i would probably say the suction pressure should be around 10-15psig. If the compressor is overheating it could be the bearings inside of the motor or it could be due to low refrigerant. If it turns out you want to replace the compressor I would make sure you don't have a leak in the evap coil. I'm not really familiar with the design of this particular vintage unit, but these are things that we check on all refrigerators with a cooling problem.

does checking for a leak in the coil just involve a close up visual inspection? I believe the evaporator coil is within the fridge part unit behind the defrost plate (this unit was one of the first to have defrost I believe)....any ideas on how the cooling (or evaporator coil) would reach the freezer?

A normal pressure on this box working correctly would be 5-7 psi.A warm box charge would be 12-15 as mentioned above.R-12 is still available although very expensive.If the system is low the leak would have to be found and repaired.If it is a bad compressor,the compressor and filter drier could be changed out to a R134a system.Your HVAC buddy may not like it,but he can do it.He can install a temporary bullet valve to check pressure.

I leak check with a sniffer (get close), soap bubbles (narrow it down), or UV dye kit for the super small leaks (months). Finding a leak visually can be near impossible, unless it is a huge leak.

I have worked in a few companies that use R414A or R414B as direct replacement for both R12 and R134. That means either gas can replace BOTH R12 and R134A. It seems to work fine. I have also used them in new R134A systems without any issues.

These gases are nice because you only have to carry one tank of refrigerant for all cases.

When the compressor shuts down feel it. If it is too hot to touch then that relay is bad. If it was low on gas it would run all the time. Try bypassing the thermostat to see if the ice box gets colder. If it does you need a new thermostat. If it don't then you know you might need to add a shot of freon in there. If you add too much she gonna lock down. The whole ice box only contains around 4 ounces or 1/3rd of a 12 oz can of freon from the automotive store. Any more than that and you gonna choke her down. Use some 12 if you can. It is still around and can be bought at O'Reily's auto parts IF you have card. Your HVAC buddy should have a freon card. Get him to buy a can. The last one I saw was at NAPA and that was $48 for a 12 oz can. That was a while back though Click pics to enlarge:

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Last summer I worked on a freezer which was not getting cold enough. Freezers and refrigerators both get charged the same way. They have different thermostats is all. Anyway I took a few photos of the repair:

About the icons: The beer is tip link, if a tech saves ya some money buy em a 6 pack. The small green square=personal message. The green dot is a link to my web page on appliance repair and other general BS I love to post. The letter sends me email.I love fan letters! LOL